1. Field of the Invention
The present invention relates to methods for fabricating crosslinked synthetic thermoplastics articles.
2. Description of the Prior Art
Crosslinked thermoplastics, having a controlled degree of crosslinking have properties of toughness, heat resistance and inertness amongst others which render them useful in various applications. However, the possibilities for fabrication of articles from crosslinked thermoplastics materials have in the past been somewhat limited.
One example of the use of crosslinked plastics materials is in the manufacture of the well-known heat-shrinkable pipe sleeves. These are usually formed as crosslinked extruded polyethylene tubes. After crosslinking, the tubes are stretched to an enlarged diameter while in a heat-softened condition and are then rapidly cooled, the stretching and rapid cooling imparting an elastic memory and a heat-shrinkable property to the tubes. Although extrusion is a feasible manufacturing method for sleeves of up to about twelve inches diameter, the existing technology sets limits on the diameters of the tubes which can economically be produced by this method. Further, the conventional type of tube-stretching apparatus cannot be conveniently or satisfactorily adapted to stretching tubes of large diameter. Pipe sleeves of greater diameter could be fabricated if it were possible to obtain a satisfactory weld between the crosslinked materials, since lengths of plastics sheeting of controlled crosslinking cut to the desired length could then be joined together end to end to provide a tubular sleeve of any desired large diameter.